24 The History of a Field newly laid down to Permanent Orass. 
plots, but it is now comparatively scarce, being mainly replaced 
by Alopecurus and Arena elatior. Lolium, too, has almost dis- 
appeared in recent years. 
Upon the whole, it may be concluded from these results 
of annual mowing for nearly thirty years, that fair quality of 
herbage, as well as full quantity, may be maintained, provided 
judgment be exercised in the manuring. Indeed, it is seen 
that the quantity of crop is gradually increasing, indicating an 
improving condition of the land under the treatment followed. 
Summary and General Conclusions. 
1. By the judicious employment of manures, both natural 
and artificial, arable land has been converted into permanent 
grass, not only without loss, but with some profit to the tenant. 
2. The important constituents, nitrogen and phosphoric acid, 
were supplied in the manures in larger quantities than they 
were removed in the crops ; but potash in only about the same 
quantity as it was removed. 
3. The application of dung, not only compensates for much 
of the exhaustion from the removal of hay, but it has a bene- 
ficial influence on the botanical character of the herbage. 
4. Although the grass has been mown every year for nearly 
thirty years, there has been a considei'able accumulation of 
fertility within the soil. 
5. Analysis has shown that there has been an increase of 
nitrogen in the surface-soil, beyond that which could be explained 
by excess supplied in manure over that removed in crops, and 
by the combined nitrogen coming down in rain, and the minor 
deposits, from the atmosphere. Part, if not the whole, of this 
increase is probably derived from the subsoil by deep-rooted 
plants, which afterwards leave a nitrogenous residue within the 
surface-soil. Or, possibly, some of it may have its source in the 
free nitrogen of the atmosphere, brought into combination within 
the soil, under the influence of micro-organisms, or other low 
forms. 
6. In laying down arable land to permanent grass, especially 
if hay is to be removed, it is essential to supply, not only nitro- 
genous, but an abundance of mineral manures, and especially 
of pota sh, a large quantity of which is removed in the crops, and 
must be returned. When the grass is not mown, but fed, the 
exhaustion is much less, but it is greater when consumed for 
the production of milk, than when for that of store or fattening 
increase. 
